I was born on the shores of the Chesapeake Bay
Maryland and Virginia have faded away
And I keep thinking tomorrow is coming today
So I am endlessly waiting...

—A. Duritz and Counting Crows, "St. Robinson and His Cadillac Dream"

Tuesday, June 29, 2010

Smoky Mountains salamanders

The Great Smoky Mountains are sometimes called "The Salamander Capital of the World". On an individual basis, salamanders (known colloquially as "spring lizards") outnumber all other vertebrates—birds, bears, fish, raccoons, humans, bats, deer, etc.—in these mountains. But it's not just that there are lots of salamanders here—there are many different kinds of salamanders here: twenty-five to thirty species, more or less. The "more or less" depends on who you ask, and when: several currently recognized species have been lumped with other, more widely-ranging species in the past, and some experts believe that there is more splitting to be done. There is a consensus, however, on one fact—the southern Appalachians, and the Smokies in particular, boast a greater diversity of plethodontids or lungless salamanders than anywhere else on the planet.

The Jordan's salamander (Plethodon jordani) is endemic to Great Smoky Mountains National Park; another species, the imitator salamander (Desmognathus imitator) is restricted to the Smokies and the adjacent Balsam Mountains. Because mountains have much in common with islands, these and several other high-elevation amphibian species may be particularly vulnerable to global warming: as the climate grows warmer, their habitat shrinks; with nowhere to go but up, they might eventually run out of space if current temperature trends are not reversed. At present, however, the Jordan's salamander is quite abundant within its limited range. The imitator is somewhat less so, but that is to be expected: it is a Batesian mimic taking advantage of its similarity in appearance to the unpalatable Jordan's; this form of mimicry is most effective when the mimic is relatively uncommon and predators are more likely to encounter the genuine (distasteful) article. Interestingly, though, only some imitators look like Jordan's; where imitator salamanders co-occur with Santeetlah salamanders (Desmognathus santeetlah) or Ocoee salamanders (D. ocoee), some individuals look like those species, which predators are not known to find aversive.

...All of which goes to illustrate a basic point about plethodontid salamanders: they're confusing as hell. Hardly any of these species are uniform in appearance, most look very similar (in some guises) to other species, many hybridize at least occasionally, and even if you're a professional herpetologist with DNA samples and a fully-equipped lab, no identification will be forever beyond dispute because salamander taxonomists agree on very little. Evolution is an ongoing process, after all, and not always conducive to neat little boxes.

With those caveats in mind, let's take a look at a couple of low- to mid-elevation 'manders.

Spotted dusky salamanders (Desmognathus conanti) are widely distributed across the Southeast, and are generally found at lower elevations in the Smokies. These were found at Laurel Creek, between Townsend and Cades Cove, on the Tennessee side of the park. (They were captured in water and placed on the sandy bank for photographic purposes, then returned to their stream.)

The next two photos might also represent D. conanti—note the similarity of color scheme if not pattern—but I believe they are in fact seal salamanders. Seal salamanders (Desmognathus monticola) also occur across the Southeast and are (surprise, surprise) quite variable. Stephen Tilley and James Huheey, authors of the handbook Reptiles & Amphibians of the Smokies, explain the common name: "Individuals are often observed during the daytime, posed on wet rocks in the spray of rushing streams with their heads raised to create profiles reminiscent of a seal's."

These next photos are definitely—well, you know, more or less definitely—seal salamanders. Still more variation here: dark grey with red markings...

...and nearly black. Incidentally, all of the photos I've attributed to seal salamanders are in situ shots from a single location on a small tributary creek of the Little River near the park entrance at Townsend.

By the way, if I've given the impression that scientists who study salamanders are contentious, it's only fair to point out that their subjects are as well. The dusky at lower left in the picture below (again, from near the park entrance at Townsend) had better be careful: seal salamanders are not at all shy about eating other salamanders, including their own kind.

A few tools to take with you for a salamandering expedition (this is not necessarily a comprehensive list):

River shoes—something that can get wet and retain good traction. Felt-soled wading boots might be the perfect choice.

Flashlight or headlamp for night-time or other low-light conditions. Red or green LEDs are the best choice, as they will not affect your night vision and tend not to disturb the animals.

Clear plastic cups—indispensable for gently catching specimens, especially in the water. All amphibians in the park are protected by law, so be sure to return each individual to its capture site.

After being fed upon by mosquitos, you'll want something to stop the itch. But I do not recommend DEET or other chemical repellents to prevent mosquito bites: salamanders and other amphibians are sensitive to such chemicals, which are readily absorbed through their moist skin. Do the 'manders a favor: deal with mosquito bites after the fact.

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Footnote: Some older reference books, for example the Peterson Field Guide to Reptiles and Amphibians by Roger Conant (from whom the spotted dusky salamander derives its specific epithet of conanti) and Joseph T. Collins, depict the Jordan's salamander as a highly variable species with a much wider range. These works pre-date the splitting of the Jordan's and several other species, including the southern grey-cheeked salamander (Plethodon metcalfi). Just another example of how scientific understanding of salamander evolution and taxonomy has itself evolved...